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Climate Change

Earth’s Tropics Growing

The changing climate affecting much of our planet continues to have weird results. The latest to become evident is the expansion of our planet’s tropical belt, according to a study published this Sunday in Nature Geoscience. 

Geographically, and thus traditionally, Earth’s tropical region is a giant belt that stretches from the Tropic of Cancer to the Tropic of Capricorn; or, in actual terms, just south of Miami to half way through Australia.

However a more scientific definition is taken by meteorologists who define the tropics as a region defined by a long term climate. It is this definition that has shown the shift in the width of the tropics towards our planet’s poles.

Independent teams set out to measure the atmospheric data available, and using four different meteorological measurements, found that the tropical belt has grown by between 2 and 4.8 degrees of latitude since 1979. This measurement translates to a total expansion – north and south – of 140 to 330 miles.

Climate scientists have long predicted that, by the end of the 21st century, a growth of the tropical belt was expected. But the growth that has taken place over the last quarter-century is puzzling, and not part of their theories.

Dian Seidel, a research meteorologist with the National Oceanic and Atmospheric Administration lab in Silver Spring, Md, is confused. “They are big changes,” she said. “It’s a little puzzling.”

And while one explanation for the expanding tropics is indeed global warming, others vie for ranking as another explanation. Depletions in the ozone layer and changes in El Nino are both other options that could explain what has happened.

So while much of the tropics are thought to be just that – tropical – there are great swathes of desert as well. One only needs to look at Australia to see that played out, with the ‘Top End’ dominated by rainforests and rainy seasons, that sit just on top of the massive desert center.

It is these desert areas that sit on the edge of tropical locations, such as the U.S. Southwest, parts of the Mediterranean, and of course Australia, that are at the most risk, according to the experts.